3M electrical tape 1339 is a plastic cored polyester film/glass filament tape coated with a pressure sensitive acrylic adhesive system. The polyester film/glass backing has excellent physical and electrical characteristics. The back side of the tape has a special coating which allows for an even, controlled unwind. - Plastic cored tape also promotes permanent anchoring in application. Typical applications for 1339 include lead anchoring, banding of coils, lead tape anchoring and other uses where tensile strength is needed.